Two-Wire Control for Multi-valve Systems

By Ed Underhill, Underhill International Corp, for LCN

 

Two-wire, or decoder, technology simplifies multi-valve irrigation by eliminating the need for a separate wire running from the controller to each valve. Instead, a single wire connects all the valves to the controller. The decoder (see inset) activates each valve when it receives the right signal?EUR??,,????'??+which all the other valve decoders will ignore. Image courtesy of Underhill, www.underhill.us

Irrigation industry analysts predict that within the next five years, two-wire control systems will be the industry standard for most mid- to large-sized residential and commercial installations in the U.S. Two-wire technology greatly simplifies multi-valve systems by letting coded signals activate valves via a single control-wire circuit.

New Applications

Two-wire is not a new technology. Attempts to simplify wire runs were made in the 1960s and 70s, primarily for golf courses. However, those early installations used DC current and had a range of problems. Two-wire systems have now been developed using AC current and advanced decoder/receiver technology. Two-wire irrigation has become the standard throughout Europe and in many areas of the developed world.

Switching to two-wire doesn?EUR??,,????'???t mean that you have to change your favorite brand of controller. Any commercial controller can easily be converted to two-wire operation. This flexibility means you and your crew can snap a decoder module into a Hunter ICC Controller ?EUR??,,????'??? or use a universal decoder module to convert any controller of your choice. You can stay with the same controller programming that you already know and don?EUR??,,????'???t need to spend time retraining on a new system.

How it Works

Two-wire controllers use just a single pair of wires that extend from the controller to each valve in the irrigation network. Instead of separate wires running to each station, there are just two wires going through the entire system, starting from the controller and running out to the last valve in the network. The two-wire path can be branched in any direction that works best on the site.

A ?EUR??,,????'??two-wire?EUR??,,????'?? decoder unit has two wires to connect it to the system circuit and two wires to attach it to its own valve.

Each valve decoder/receiver has its own unique ?EUR??,,????'??address,?EUR??,,????'?? corresponding to the station number. During installation each valve decoder/receiver is programmed in the field with that specific address.

Ed Underhill has worked in the landscape irrigation industry for more than 20 years and is president of Underhill International Corp. in Lake Forest, Calif.

A Quick Two-Wire System Overview

?EUR??,,????'???? Only one pair of two wires run from the controller to all valves in the system.
?EUR??,,????'???? 24 VAC power and address signal are sent over the same pair of wires.
?EUR??,,????'???? Valves are installed along the two-wire path. Each valve has an individual ?EUR??,,????'??decoder?EUR??,,????'?? (or receiver switch) installed within it.
?EUR??,,????'???? Every valve decoder/receiver has a unique address that identifies it to the controller. Signals are sent to each valve decoder/receiver from the controller telling it when to open or close.
?EUR??,,????'???? Any existing or new commercial controller can easily be converted to two-wire operation with up to 63 stations.

Two-wire valve decoders were pioneered for large golf course systems but are becoming increasingly popular on residential and commercial landscapes. Photo courtesy of Rain Bird

Irrigation Insights

3/4 and 1: Inch, the sizes available for anti-siphon valves. Anti-siphon valve must be installed above ground and must be at least six inches higher than the highest sprinkler head.

5: GPM, the minimum flow recommended when using automatic valves. Many automatic valves won't work at all at flows below 5 GPM. Source: Jess Stryker?EUR??,,????'???s Irrigation Tutorials